The overarching approach of the proposed research is to use the comparative method to understand leptin's role in the development of human diabetes and obesity. We will use the zebra fish model to test specific hypotheses about leptin function. In our last award, we established that leptin is required for normal zebra fish development, as zebra fish embryos with reduced leptin do not absorb yolk, have reduced sensory structures (eyes and inner ear), abnormal notochord, impaired cardiac function and lower metabolic rate. In this renewal proposal we will address two Specific Aims that build on our previous work: I- We will test the hypothesis that increased leptin titer activates lipid mobilization from liver in adult zebra fish. We will increase and decrease leptin titer in adult zebra fish and test for up-regulation of lipid catabolism in liver. II: We will test the hypothesisthat expression of the leptin receptor overlapping transcript (LEPROT) modulates leptin sensitivity in zebra fish. LEPROT negatively regulates cell-surface expression of the leptin receptor in humans and other mammals. Its coding sequence is contained within the leptin receptor gene via an alternate start site, and its expression is regulated by the leptin receptor promoter. In fishes, LEPROT's primary structure is conserved, but the gene is separated from the leptin receptor. We will test whether LEPROT function is conserved in fishes. The proposed research will be conducted with substantial consideration toward providing training opportunities for young scientists. Funds are requested to support graduate students and undergraduate students, and the lead investigators, graduate students, and undergraduate students will form a mentoring team for high school student volunteers. Students will be involved in hands-on research, each with their own distinct project that contributes to the overall goals of the proposal. The PI and Co-investigator have an excellent record of sponsoring undergraduate research. Independent research projects using the zebra fish model are central to their advanced undergraduate classes (e.g. Cell Physiology with an annual enrollment of 50), and the PI rewrote all introductory Biology laboratories to include undergraduate research in each laboratory. The PI also started an undergraduate research symposium in his home department (now in its 7th year) and both PI and Co-PI sponsor several Honors thesis research projects in their laboratories annually. Finally, both investigators have been successful in attracting underrepresented students into their research programs, and the PI is a member of an NSF-sponsored project dedicated to increasing representation of women and minorities in STEM disciplines (Project IDEAL). PUBLIC HEALTH RELEVANCE: The proposed studies investigate function of the hormone leptin in the zebra fish model organism. Results of these studies may lead to greater understanding of how obesity, metabolic syndrome, and diabetes develop in humans, as well as potential therapies for those diseases.